This invention relates to vane axial fan assemblies, and in particular, to an improvement in the design of the discharge plenum or chamber adapted for receiving the air discharged from the blades of the fan assembly.
The utilization of large fans, such as vane axial and centrifugal fans, in many different applications is well known to the art. For example, such fans may be employed in central station air handling equipment employed in air conditioning systems for multi-story buildings such as offices, schools and the like. Each of the two types of fans mentioned above have different characteristics which make each suitable for different applications. As an example, a vane axial fan with controllable pitch blades has certain characteristics that provide operational cost savings at partial loads in a variable volume air supply system when compared to a centrifugal fan; however, the cost of a centrifugal fan is somewhat lower than the cost for a comparable vane axial fan. In addition, the centrifugal fan provides a more compact assembly and provides greater flexibility when compared to a standard vane axial fan assembly. The compactness and flexibility inherent in a centrifugal fan when compared to a vane axial fan is primarily due to the Archimedean-shaped scroll normally employed for receiving the air discharged from the blades of the fan. The discharge chamber or plenum typically employed with a vane axial fan is generally an elongated cylindrically shaped member of substantial axial length.
In many applications, it has been found advantageous or desirable to employ a vane axial fan assembly. However, in many of such applications, the utilization of a vane axial fan has not been possible due to the fan assembly's inherent lack of flexibility and compactness. Accordingly, centrifugal fans have been utilized to a much greater extent than have vane axial fans.
To achieve the compactness and flexibility offered by a centrifugal fan, a vane axial fan has been combined with essentially a centrifugal type Archimedean-shaped discharge scroll. There is no known prior art wherein this combination has been previously used.